The Internet is a packet based network transporting many different types of telecommunications traffic, such as voice, data, and multimedia traffic, which originates from a large variety of applications. Different types of traffic have different quality of service (QoS) demands. For voice traffic a small and uniform packet delay is particularly important, while small packet loss is the most important requirement for data traffic. Furthermore, service providers are interested in offering services with different QoS that allow them to satisfy the varying needs of their customers and to maintain a differentiated pricing scheme. Therefore several mechanisms for providing different QoS to different users and traffic flows in packet based networks such as the Internet have been developed.
The international patent application WO02/25867 describes a radio access network that provides different priority classes to different packet data connections with a user equipment. The priority class of a data connection may be dynamically adjusted by a control node in accordance with a throughput criterion which is communicated to the control node by the user equipment.
The IETF (Internet Engineering Task Force) has developed the Integrated Services (IntServ) architecture which is described in IETF RFC 1633. The IntServ architecture uses an explicit mechanism to signal per-flow QoS requirements to network elements such as hosts and routers. There are a number of drawbacks associated with IntServ. IntServ requires maintenance and control of per-flow states and classification. Network resources are reserved on a per-flow basis which introduces scalability problems at the core networks where the number of processed flows often is in the range of millions. Therefore it is only practical to use the IntServ architecture in small access networks where the number of flows is modest.
To overcome the scalability and complexity problems of IntServ the IETF introduced the Differentiated Services (DiffServ) architecture, described in IETF RFC 2475. Traffic through network core routers implementing DiffServ is treated on an aggregate basis. Traffic entering a network is classified and assigned to different behaviour aggregates. Each behaviour aggregate is identified by a single DS (Differentiated Services) codepoint. When the traffic is classified packets are marked with a particular DS codepoint which is placed in a DS field in the IP (Internet Protocol) header. Within the core of the network, a packet is forwarded according to a per-hop behaviour (PHB) associated with the DS codepoint of the packet. A PHB determines the externally observable forwarding behaviour (such as forwarding delay and packet loss) of a node at different load levels. PHBs are logical network resources that govern the use of underlying physical network resources. Thus a PHB can be seen as a partial network resource, which defines a subset of a total network resource.
The international patent application WO02/11461 is one example of a document that describes a DiffServ system. It discloses a method and arrangement for providing dynamic quality of service by means of a bandwidth broker in an IP Network that includes a DiffServ architecture. The bandwidth broker may obtain resource availability information by communication only with border routers of a DiffServ domain.
Another example of a document that discusses a DiffServ implementation is the international patent application WO02/080013, which describes dynamic resource allocation that provide differentiated services over a broadband communication network that includes a satellite.
When a service provider sells a bearer service to an end user the service is usually specified. The service may be specified by a Service Level Specification (SLS) that includes QoS requirements for the service. Thus SLSs may be used to define different classes or levels of service. In order to fulfil the QoS requirements of the SLS the allocation of resources assigned to the traffic associated with the SLS is crucial. Today the mapping of SLSs to network resources is usually made semi-permanently as part of the provisioning and configuration of a network, see IETF RFC 3086. The mapping is set up to suit an expected mix of traffic.
In traditional networks, the traffic characteristics are fairly well known. In future multi-service networks and multi-access networks, traffic characteristics will be dynamic due to changes in user behaviour, introduction of new applications, etc. Moreover, these changes imply that the network must be flexible in terms of resource allocation to different QoS classes. New techniques for managing networks efficiently will therefore be needed.